have (someone) in the palm of (one's) hand
To have great influence over someone. If you want to have someone in the palm of your hand, flattery always helps.
have (or hold) someone in the palm of your hand
have someone under your control or influence.have somebody in the ˌpalm of your ˈhand
have somebody completely under your control or influence: Her boyfriend will do anything for her; she’s got him in the palm of her hand.